Process of recovering and purifying dilute sulphuric acid from acid sludge



Patented Jan. 27, 1931 uuirsn STATES PATENT eF iri FRANKLIN KIMBALL, or LQNG BEACH; CALIFORNIA rRooE'ss or RECOVER-ING- Ann runrrviue :ornu'rn sunrrrunrc Ac'I'i) rnoM Aoin SLUDGE r r No Drawing. Application filed. September My invention relates to the treatment of acid sludge obtained by the action oi sulphuric acid on petroleum oils or distillates, for recovering the sulphuric acid therefrom.

5 In the various processes previously employed for recovering sulphuric acid from the acid sludge to recover the dilute sulphuric It is well known that sulphuric and recovered by this and similar A recesses is imacid.

pure, and hence it is a purpose oi my invention to provide a process of treating the acid sludge to recover relatively more pure dilute sulphuric acid.

lVhen dilute sulphuric acid derived from acid sludge is concentrated by evaporation of the water therein, about two per cent by weight of finely divided carbon results in the concentratedacid and as a result of experiment I have found that merely upon dilution of the sludge with water hydrolysis is effected, oil is liberated and most of the carbon suspends itself Within the oil, and therefore can be removed from the dilute acid by draw- .so ing oil the-oil; In this manner, a partial purification of the dilute sulphuric acid is effected. Asis well known, acid sludge derived from the use of sulphuric acid containing carbon is very refractory. Hence, if a major portion of the carbon can be removed from-the acid sludge prior to that hydrolyzing treatment which consists of subjecting the mass to heat and pressure, not only is e1 fccted a preliminary purification'of the sul-' phuric acid, but there is facilitated a more eflicient hydrolysis eiiected by heat and pressure, and in consequence, the final dilute sulphuric acid recovered is of greater degree of purity and j therefore produces higher yield upon concentration. In my process,l effect this preliminary removalof carbon and oil by the preliminary elimination of the presence or" a major portion of the oil, for the carbon which is formed upon heating the oil in the hydrolyzing treat- 30, 1929. Serial No. 396,402.

ment, is reduced to a minimum as to quantity in wow of the small amount 'ofoil remaining iuthe af'eid sludge. In reducing the, amount 1 acid sli'idges that are found *toseparate oil and dilute sulphuric acid upon diluting with water, in givinga practical illustration of my process I will describe it in connection with the treatment of acid sludge derivedfrom' the acid treatment of crackedgasoline, but it is to be understood that my invention is not limited or. restricted tothis form of acid sludge nor to the precise quantities, proportions, temperature and pressure recited/ In the application) oi my process to cracked gasoline, 250 tons of cracked gasoline may be treated with 5 tons of 66- Baum sulphuric acid containing about of fine carbon yielding 7 tons otl0 Baume acid sludge. My process in respect to-acid" sludge derived in this manner comprises dill lut-ing the acid sludge by mixing therewith in a suitable vessel, 3 tons ofwater. *T'his mixing operation is done by admitting the watt-n to the bottom of thevessel containing the acid sludge. After settling about hours. there is found to be 2 tons of oil floating on 8 tons of 33 Ba-uin'gravity sulphuric acid. The sulphuric acid is drawnfrom the'vesseland placed in a suitable and heat insulated drum of such capacity that the acid does'not' completely fill it but leaves an air space there- Y above. By admitting steamto the bottom of the drum so that it passes upwardly through the acid, the air above tlie acid is driven from the drum through a suitable vent, and until the tei'nperature at the top ofthe driun is about 200 F.,'indicating the absenee of air. T he vent'isnow closed andthe heating continued until the pressure exceeds 50 pounds per square inch gauge pressure, and the temperature exceeds 300 F. Once this pressure and temperature is exceeded, the steam supply is cut off, and the'heated acid allowed to settle for about one hour. WVe

now find that the drum contains 8 A tons of 32 Baum gravity sulphuric acid and one half ton of oil separated from the acid. The final separation of the oil from the acid is accomplished by Withdrawing either from the drum. V j

Although I have herein shown and described only one process of recovering and purifying dilute sulphuric acid from acid sludge embodying my invention, it is to be understood that various changes and moditications may be made herein Without departing from the spirit of the invention and the spirit and scope of the appended claims.

I claim: 7 w

1. A process of recovering and purifying dilute sulphuric acid from acid sludge, which consists in the additionoiiwater to effect the separation of oil, removing the separated oil from the diluteacid, expelling the fixed gases from the dilute acid, subjecting the dilute acid to a temperature above its atmospheric boiling point to effect separation of the remaining oil, and finally separating the dilute acid from the separated oil.

25A process of recovering and purifying dilute sulphuric acid from acid sludge, which consists in the addition of Water to effect the separationof oil, removing the separated oil from the dilute, acid, subjecting the dilute acid toa temperature above its atmospheric boiling point to effect a separation of the remaining oil, and finally separating the dilute acid from the separated oil. 7

3. A process'of recoveringand purifying dilute sulphuric acid from acid sludge, which consists in the addition of water to effect the separation of oil until the 33 Baum grav-- ity is reached, removing the separated oil from the dilute acid, expelling the fixed gases from the dilute acid, subjecting the dilute acidto a temperature of from between 300 to 320 F. under a pressure of between and pounds gauge to effect separation of the remaining oil, and finally separating the dilute acid from the separated oil.

4. A process of recovering and purifying dilute sulphuric acid from acid sludge, which consists in the addition of water to effect the separation of the oil until the-33 Baum gravityis reached, ren'iovin'g the separated on from the dilute acid, subjecting the dilute acid to a temperature of from between t 800 to 320 F. under a pressure of between 50 and 60 pounds gauge to effect separation of the reinainlng o1l, and finally separating the dilute acid frointhe separated oilj FRANKLIN E. KIMBALL. 

